The present invention relates to a downconverter, a downconverter IC, and a method for controlling the downconverter, and in particular, to a downconverter for down-converting a polarized wave signal as received, a downconverter IC, and a method for controlling the downconverter.
For converting the frequency of a satellite wave as received into an intermediate frequency (hereinafter referred to also as an IF frequency) that is transmittable via a cable, use is being made of a low noise block downconverter (LNB downconverter: Low Noise Block downconverter).
FIG. 14 is a block diagram for describing a satellite reception converter (downconverter) disclosed in Patent Document 1. With the satellite reception converter shown in FIG. 14, a BS signal of a horizontally polarized wave or a vertically polarized wave, received via a parabola antenna (not shown), is inputted thereto from BS signal terminals 221, 222, respectively, and amplifier circuits 223, 224, in an initial stage, together with an amplifier circuit 225, in a second stage, are disposed in a back stage of the BS signal terminals 221, 222, respectively. The respective amplifier circuits 223, 224, in the initial stage, amplify the BS signal of the horizontally polarized wave or the vertically polarized plane wave, inputted from the BS signal terminals 221, 222, respectively. Then, the amplifier circuit 225, in the second stage, further amplifies an output of either the amplifier circuit 223 or the amplifier circuit 224, in the initial stage.
The amplifier circuits 223 to 225 each are a low-noise high-frequency amplifier for operating at a high frequency by use of a high electron mobility transistor (HEMT: High Electron Mobility Transistor), and so forth. In order to enable the amplifier circuit 223 or the amplifier circuit 224 to receive either the horizontally polarized wave or the vertically polarized plane wave, it is necessary to selectively switch between respective voltages supplied to these amplifier circuits. For this reason, selective switching between the voltages to be supplied to the amplifier circuit 223 and the amplifier circuit 224, respectively, is made in a switching circuit 310 incorporated in a satellite reception converter IC 201. More specifically, a voltage necessary for the amplifier circuit 223 or the amplifier circuit 224 is supplied from terminals 211, 212, or terminals 213, 214, respectively, according to whether a received BS signal is the horizontally polarized wave or the vertically polarized wave. Further, in order for the amplifier circuit 225, in the second stage, to amplify the BS signal of either the horizontally polarized wave or the vertically polarized wave, a necessary voltage is supplied thereto from terminals 215, 216, respectively, at all tines while the BS signal is being received.
An output of the amplifier circuit 225 is further amplified by an amplifier circuit 311 incorporated in the satellite reception converter IC 201 to be converted into a BS-IF signal at an intermediate frequency by a frequency converter 312. The BS-IF signal is further amplified by a back-stage amplifier circuit 313, and subsequently, a DC component is removed from the BS-IF signal by a capacitor 204 to be sent out to a BS tuner (not shown) via a cable (not shown).
Further, a PLL circuit 314 including a local oscillation circuit outputs a local oscillation signal for converting low band frequencies in a range of 10.7 to 11.7 GHz and high band frequencies in a range of 11.7 to 12.75 GHz in received frequencies in a range of 10.7 to 12.75 GHz into the frequency of the BS-IF signal.
A DC voltage signal for controlling switching of a polarized wave received from the BS tuner is inputted to the switching circuit 310. More specifically, the DC voltage signal at either 13V or, doubling as a power supply voltage, is inputted to the switching circuit 310, and the switching circuit 310 detects magnitude of the DC voltage signal that is inputted, thereby making a decision as to which of the amplifier circuits 223, 224 in the initial stage is put to use.
A voltage generation source 315 for generating plus and minus voltages according to the magnitude of the DC voltage signal detected by the switching circuit 310 provides either the amplifier circuit 223 or the amplifier circuit 224, and the amplifier circuit 225, with the plus and minus voltages via the terminals 211 to 216, respectively.
The high electron mobility transistor (HEMT) for use in the amplifier circuits 223 to 225, respectively, is normally activated by supplying a gate terminal with the minus voltage, and supplying a drain terminal with the plus voltage. For example, in the case of using the amplifier circuit 223, the satellite reception converter IC 201 generates the minus voltage from the terminal 213, supplying the gate terminal of the HEMT with the minus voltage. The satellite reception converter IC 201 concurrently generates the plus voltage from the terminal 214, supplying the drain terminal of the HEMT with the pus voltage. As to voltage supply to the amplifier circuit 224 that is out of use at this time, a voltage for inactivating the HEMT for use in the amplifier circuit 224 is supplied from the terminals 211, 212, respectively.
With such a configuration as described above, an output signal of the amplifier circuit 223 is supplied to the amplifier circuit 225. The amplifier circuit 225 is also activated as is the case with the amplifier circuit 223, and the minus voltage outputted from the terminal 215 of the satellite reception converter IC 201 is supplied to the gate terminal of the HEMT. The plus voltage outputted from the terminal 216 is concurrently supplied to the drain terminal of the HEMT. By so doing, the BS signal amplified by the amplifier circuit 225 is supplied to the amplifier circuit 311 of the satellite reception converter IC 201.
In the case of using the amplifier circuit 224, the satellite reception converter IC 201 generates the minus voltage from the terminal 211, supplying the gate terminal of the HEMT with the minus voltage. The satellite reception converter IC 201 concurrently generates the plus voltage from the terminal 212, supplying the drain terminal of the HEMT with the plus voltage. At this time, a voltage for inactivating the HEMT for use in the amplifier circuit 223 is supplied to the amplifier circuit 223 that is out of use.
With the satellite reception converter shown in FIG. 14, the switching circuit 310 for switching between the amplifier circuit 223, and the amplifier circuit 224 is incorporated in the satellite reception converter IC 201. That is, the satellite reception converter IC 201 is provided with the circuits for generating the minus voltage for activating the amplifier circuit 223, or the amplifier circuit 224 in order to receive either the horizontally polarized wave, or the vertically polarized plane wave.
Further, in Patent Document 2, there has been disclosed a technology relating to a downconverter capable of enhancing isolation of LNBs in whole. In Patent Document 3, there has been disclosed a technology relating to a tuner device capable of single-handedly receiving respective signals from a plurality of channels. In Non-patent Document 1, there has been disclosed a technology relating to a universal single type LNB.
[Patent Document 1]    Japanese Unexamined Patent Publication No. 2010-268296
[Patent Document 2]    Japanese Unexamined Patent Publication No. 2002-190749
[Patent Document 3]    Japanese Unexamined Patent Publication No. 2003-198401
[Non-patent Document 1]    Tino Copani, “A 12-GHz Silicon Bipolar Dual-Conversion Receiver for Digital Satellite Applications”, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 40, NO. 6, JUNE 2005